CN107541681B - The ferrite-group stainless steel of the excellent in low temperature toughness of welding point - Google Patents

The ferrite-group stainless steel of the excellent in low temperature toughness of welding point Download PDF

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Publication number
CN107541681B
CN107541681B CN201710120948.4A CN201710120948A CN107541681B CN 107541681 B CN107541681 B CN 107541681B CN 201710120948 A CN201710120948 A CN 201710120948A CN 107541681 B CN107541681 B CN 107541681B
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stainless steel
welding point
ferrite
group stainless
formula
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CN107541681A (en
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金钟哲
郑壹鄼
金善求
李元培
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Posco Holdings Inc
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Posco Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
    • B23K35/3053—Fe as the principal constituent
    • B23K35/308—Fe as the principal constituent with Cr as next major constituent
    • B23K35/3086—Fe as the principal constituent with Cr as next major constituent containing Ni or Mn
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Nonmetallic Welding Materials (AREA)

Abstract

The present invention discloses a kind of ferrite-group stainless steel of welding point excellent in low temperature toughness.Ferrite-group stainless steel according to an embodiment of the invention, in terms of weight %, it include: Cr:9~30%, N: less than 0.015%, Al:0.005~0.04%, Ti:0.1~0.5%, surplus Fe and other inevitable impurity, and meet following formula (1), and including maximum gauge be 0.05 to 5 μm, have 9/mm2The Al-Ca-Ti-Mg-O system oxide of above distribution density.Therefore, the size and distribution density of Al-Ca-Ti-Mg-O system oxide in the base material of stainless steel can be controlled, thus, it is possible to sufficiently refine welding point solidified structure, so as to improve the mouldability and welding point low-temperature flexibility of ferrite-group stainless steel, Ti > (0.0065Cr+0.38N+8.3Al) --- --- formula (1).

Description

The ferrite-group stainless steel of the excellent in low temperature toughness of welding point
Technical field
The present invention relates to a kind of ferrite-group stainless steels, and more specifically, the low-temperature flexibility for being related to a kind of welding point is excellent Different ferrite-group stainless steel.
Background technique
Ferrite-group stainless steel is mainly used for automobile exhaust system accessory, mainly forms and weld institute by punch process Processed goods is stated, or makes final products by carrying out expander and molding to soldered conduit.Therefore, automobile exhaust system It is, for example, welding point processing characteristics with the important requirement condition of ferrite-group stainless steel.
Generally, the welding process of ferrite-group stainless steel is using electric arc thermal melting base material, and the metal melted at this time is quick It cools down and forms solidified structure, the grain size of this solidified structure and the processability of shape Welded Joints have a great impact.
In particular, since the heat input of the welding method for automobile exhaust system is big, range is wide, the crystal grain of welding point Coarsening causes to increase with the probability being cracked when post-processing.Moreover, the coarsening of welding point crystal grain, which has, hinders The feature of low-temperature flexibility characteristic, in particular, in winter converted products when, welding point cracking frequency sharply increases.
Therefore, it could be aware that, in order to meet the welded joint performance of automobile exhaust system accessory, need refined molten connector Solidified structure.
Current solidified structure refinement technology has low temperature casting process and electromagnetic agitation (Electro Magnetic Stirring) method etc., although however, this technology can refine the solidified structure of base material, when welding, connects melting The refinement of the solidified structure of head is but without effect.
In particular, the curing condition of welding point cooling velocity compared with general curing condition is fast, it is easily grown to column branch Therefore crystalline substance has the coarsening feature of solidified structure.It therefore, can be non-by encouraging in order to refine welding point solidified structure Homogeneous nucleation passes through remaining oxide when the melting connector melted again when welding solidifies again to realize, occur it is heterogeneous at Core, to promote the nucleation and growth of equiax crystal, prediction solidified structure will be refined.
One example of the nonhomogen-ous nucleation as the oxide using ferrite-group stainless steel, it is public in existing literature 1 The technology using Al-Mg system field trash refinement base material tissue has been opened, has been disclosed in existing literature 2 to include the compound of Ti and Ca The technology of stainless steel is manufactured based on oxide.It can be by generating MgO, MgO-Al in addition, being disclosed in existing literature 32O3 Ensure base material tissue.
However, the refinement that focuses on base material solidified structure of the existing literature 1 to existing literature 3, and for weldering The composition of the oxide of connector solidified structure or size, the quantity of oxide do not consider.In particular, with regard to welding point and Speech, since differently, melting temperature is high with general cast sturcture, it is thus possible to effect is lost because of melting again for oxide, and And since cooling velocity is fast, there is the feature for the size for needing to control the oxide for refinement.Therefore, just described special For sharp document, it is not used to the preferred method of the solidified structure refinement of welding point.
Existing technical literature
[patent document]
(existing literature 1) Korean Patent Laid the 10-2011-0074217th (on June 30th, 2011 is open)
(existing literature 2) Japanese Laid-Open Patent Publication the 2000-001715th (on January 7th, 2000 is open)
(existing literature 3) Japanese Laid-Open Patent Publication the 2001-254153rd (on September 18th, 2001 open)
Summary of the invention
(1) technical problems to be solved
The one kind that is designed to provide of the embodiment of the present invention can be solidifying by the base material tissue and welding point of stainless steel Gu tissue refines to improve the ferrite-group stainless steel of the mouldability of stainless steel and the low-temperature flexibility of welding point.
(2) technical solution
The ferrite-group stainless steel of welding point excellent in low temperature toughness according to an embodiment of the invention, with weight % Meter, comprising: Cr:9~30%, N: less than 0.015%, Al:0.005~0.04%, Ti:0.1~0.5%, surplus Fe and its His inevitable impurity, and meet following formula (1), and including maximum gauge be 0.05 to 5 μm, with 9/mm2 or more The Al-Ca-Ti-Mg-O system oxide of distribution density.
Ti > (0.0065Cr+0.38N+8.3Al) --- --- formula (1)
Also, according to one embodiment of present invention, may include: C: less than 0.02%, Si:0.01~0.5%, Mn: 0.01~0.5%, S: less than 0.01%, P: less than 0.04%, Ca:0.0001~0.003%.
It also, may include according to one embodiment of present invention, selected from by Mo:0.1~2.0%, Ni:0.1~2.0% And one or more of the group that Cu:0.1~2.0% is formed.
Also, according to one embodiment of present invention, Al-Ca-Ti-Mg-O system oxide meets following formula (2),
% (TiO2)+% (CaO) >=40------ formula (2).
Also, according to one embodiment of present invention, Al-Ca-Ti-Mg-O system oxide meets following formula (3) extremely (5),
% (TiO2)+% (CaO)+% (Al2O3) >=80------ formula (3)
(% (TiO2)+% (CaO))/(% (TiO2)+% (CaO)+% (Al2O3)) >=0.4------ formula (4)
0.3≤% (CaO)/% (TiO2)≤0.8------ formula (5).
Also, according to one embodiment of present invention, the average grain diameter of welding point solidified structure is 90 μm or less.
Also, according to one embodiment of present invention, welding point ductile-brittle transition temperature (DBTT) be -65 DEG C with Under.
(3) beneficial effect
The embodiment of the present invention can be by controlling in base material of the components system of ferrite-group stainless steel to control stainless steel The size and distribution density of Al-Ca-Ti-Mg-O system oxide, and thus, it is possible to sufficiently refine welding point solidified structure, thus The mouldability of ferrite-group stainless steel and the low-temperature flexibility of welding point can be improved.
Detailed description of the invention
Fig. 1 is the photo for showing the welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention.
Fig. 2 is the photo for showing the welding point solidified structure of the ferrite-group stainless steel of comparative example.
Fig. 3 is shown in the crystal grain of welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention The chart of the composition analysis result of the nucleation field trash of center portion.
Fig. 4 is the average crystalline substance for showing the welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention The chart of grain size measurement result.
Fig. 5 is the putting down based on welding point solidified structure for showing the ferrite-group stainless steel of one embodiment of the present of invention % (CaO+TiO in the average composition ingredient of the oxide of equal grain size2) measurement result chart.
Fig. 6 is the measurement knot for showing the welding point impact energy of the ferrite-group stainless steel of one embodiment of the present of invention The chart of fruit.
Fig. 7 is the welding point ductile-brittle transition temperature for showing the ferrite-group stainless steel of one embodiment of the present of invention Spend the chart of the measurement result of (DBTT).
Specific embodiment
In the following, the embodiment of the present invention is described in detail referring to attached drawing.The following examples are in order to the present invention Person of an ordinary skill in the technical field sufficiently passs on thought of the invention and proposes.The present invention is not limited to refer to herein Embodiment, can embody otherwise.In order to clearly state the present invention, the portion unrelated with explanation is omitted in figure Point, and in order to make it easy to understand, can more or less amplify the size for indicating constituent element.
The ferrite-group stainless steel of the excellent in low temperature toughness of the welding point of one embodiment of the present of invention, with weight % Meter, comprising: Cr:9~30%, C:0.02% or less, N:0.015% or less, Al:0.005~0.04%, Si:0.01~ 0.5%, Mn:0.01~0.5%, S:0.01% or less, P:0.04% or less, Ca:0.0001~0.003%, Ti:0.1~ 0.5%, surplus Fe and other inevitable impurity.
The content of Cr is 9~30%.When the content of Cr is less than 9%, the corrosion resistance as stainless steel is insufficient, when being more than When 30%, mouldability is reduced, and therefore, content range is preferably 9~30%.
The content of C is 0.02% or less.C is interstitial element, when additive amount increases, with the reduction of elongation percentage, molding When processability reduce, therefore by maximum constraint be 0.02%.Preferably, it is contemplated that the cost during steelmaking operations will contain 0.002% is limited under amount.Therefore, content range is preferably 0.002~0.02%.
The content of N is 0.015% or less.N is interstitial element, when additive amount increases, with the reduction of elongation percentage, molding When processability reduce, therefore by maximum constraint be 0.015%.Preferably, it is contemplated that the expense during steelmaking operations will contain 0.002% is limited under amount.Therefore, content range is preferably 0.002~0.015%.
The content of Al is 0.005~0.04%.Al is necessary element as deoxidant element, still, when a large amount of additions When, due to forming invalid oxide, it is unable to control the coarsening of welding point crystal grain, therefore, it is difficult to improve low-temperature flexibility.Cause This, it is contemplated that deoxidation effect includes at least 0.005% or more, and for the refinement of welding point crystal grain, by maximum constraint It is 0.04%.Therefore, content range is preferably 0.005~0.04%.
The content of Si is 0.01~0.5%.Si is the element that adds from the aspect of corrosion proof, when less than 0.01% When, it is difficult to sufficient corrosion resistance is obtained, however, the impurity of material increases when more than 0.5%, causes elongation percentage and processing hard Changing index (n value) reduces, and Si system field trash increases, and processability is deteriorated.Therefore, content range is preferably 0.01~0.5%.
The content of Mn is 0.01~0.5%.Mn is the element of addition from the aspect of corrosion resistance, when less than 0.01% When, it is difficult to sufficient corrosion resistance is obtained, however, the impurity of material increases when more than 0.5%, leads to elongation percentage and corrosion resistance It reduces.Therefore, content range is preferably 0.01~0.5%.
The content of S is 0.01% or less.From the aspect of corrosion proof, the content of S is preferably low content.Preferably, it examines Consider the cost during steelmaking operations, 0.0001% will be limited under content.Therefore, content range is preferably 0.0001 ~0.01%.
The content of P is 0.04% or less.From the aspect of corrosion resistance, the content of P is preferably low content.Preferably, consider Cost during to steelmaking operations will be limited to 0.0001% under content.Therefore, content range be preferably 0.0001~ 0.04%.
The content of Ca is 0.0001~0.003%.Ca is the weight to form effective oxide of the invention as deoxidant element Element is wanted, however, inhibit the formation of effective oxide, and be also unfavorable for corrosion resistance when largely including, it therefore, will be maximum Value is set to 0.003%, and minimum value is set to the minimum value for being used to form effective oxide, i.e., 0.0001%.Therefore, content model Enclose preferably 0.0001~0.003%.
The content of Ti is 0.1~0.5%.For Ti, the precipitation for inhibiting corrosion resistance to reduce preferentially is formed in conjunction with C, N Object, however, being unable to reach the Al-Ca-Ti-Mg-O system oxide as the purpose of the present invention when the content of Ti is less than 0.1% Component, size and distribution density, because of the high-melting-point nitride of such as TiN etc., finally produced when the content of Ti is more than 0.5% The linear discontinuities as caused by field trash occur in product, when manufacturing continuous casting billet, spray nozzle clogging, processability are reduced.
It is the most important element for determining effective oxide of the invention for Ti, it can by a series of experiment It determines to meet the component of the effective oxide in the aftermentioned present invention and the smallest Ti content of size and distribution density.This hair The minimum value of bright middle considered Ti is influenced by Cr content in the range of the component and N content and Al content is met, And following formula (1) should be met.
Ti > (0.0065Cr+0.38N+8.3Al) --- --- formula (1)
When being unsatisfactory for the formula (1), it is unable to reach the component, size and distribution of the oxide as the purpose of the present invention Density.That is, the average grain diameter with the solidified structure of the stainless steel welded joint for the range for being detached from the formula (1) is more than 100 μm, ductile-brittle transition temperature (DBTT) is more than -65 DEG C, and low-temperature flexibility is caused to reduce.
Also, the ferrite-group stainless steel of the excellent in low temperature toughness of the welding point of one embodiment of the present of invention, with weight Measure % meter, including selected from one of group for being made of Mo:0.1~2.0%, Ni:0.1~2.0% and Cu:0.1~2.0% with On.
The content of Mo is 0.1~2.0%.Mo is the corrosion proof constituent for increasing stainless steel, can additionally be added, When being excessively added, impact characteristics can be made to reduce, increase the danger being broken, and material cost increase when processing, therefore, In view of the problem, the constituent ratio of Mo is preferably limited to 0.1 to 2.0% in the present invention.
The content of Ni is 0.1~2.0%.Ni is to improve corrosion proof element, and when a large amount of additions, not only hardening, is gone back There is the worry that stress corrosion cracking occurs, it is therefore preferable that being 2.0% or less.
The content of Cu is 0.1~2.0%.In order to improve corrosion resistance, Cu preferably includes 0.1~1.0 weight % or less.So And when more than 1.0 weight %, processability reduces.
Ferrite-group stainless steel can will meet the stainless steel of the components system through electric furnace (EAF), refining furnace (AOD), group Point adjustment (LT), tundish (Tundish), continuous casting process and after manufacturing steel billet, hot rolling, annealing, cold rolling, annealing are made cold Roll roll bending (coil).
Fig. 1 is the photo for showing the welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention. Fig. 2 is the photo for showing the welding point solidified structure of the ferrite-group stainless steel of comparative example.Fig. 3 is to show of the invention one The component analysis knot of the nucleation field trash of the crystal grain central part of the welding point solidified structure of the ferrite-group stainless steel of embodiment The chart of fruit.
Referring to figs. 1 to Fig. 3, the reason of solidified structure difference in order to confirm welding point region, electron microscope is utilized The nucleation field trash of precision observation equiax crystal central part, result are observed such as the spherical oxide of embodiment or oxidation in Fig. 3 Object and TiN around the oxide, observing the spherical oxide by transmission electron microscope precision can be seen that the oxidation Object is with the CaO-TiO of crystalline2Phase and amorphous Al2O3The form of-MgO phase exists.In contrast to this, in a comparative example, Although it has been confirmed that there is no oxide or in TiN, there are spherical oxides, and most of oxide is with Al2O3-MgO The form of phase exists.Therefore, from the result it has been confirmed that the equiax crystal of the solidified structure as welding point or TiN at Epipole (site), CaO-TiO2Compared to advantageous.
According to an embodiment of the invention, including Al-Ca-Ti-Mg-O system for refining the scheme of welding point solidified structure Oxide, the oxide will not be melted in molten steel again in high sweating heat, and be remained with solid phase, when melting for welding point When melting metal freezing, it is capable of providing Delta (δ)-ferritic effective nucleating point.Also, it confirms to make the oxidation Object sufficiently refines the solidified structure of welding point, therefore, to assure that its size and distribution density.
Therefore, the ferrite-group stainless steel of the excellent in low temperature toughness of the welding point of one embodiment of the present of invention includes most Major diameter is 0.05 to 5 μm, has 9/mm2The Al-Ca-Ti-Mg-O system oxide of above distribution density.
The maximum gauge of the Al-Ca-Ti-Mg-O system oxide included by the ferrite-group stainless steel is less than At 0.05 μm, oxide is too small, can not play the role of Delta (δ)-ferritic effective nucleating point, when more than 5 μm, promotees Into flotation, residual quantitative change is few, can not play the role of the crystalline substance for leading to welding point solidified structure as the sufficient of nucleating point Grain average diameter is more than 90 μm.
When the Al-Ca-Ti-Mg-O system oxide that the ferrite-group stainless steel includes distribution density less than 9/ mm2When, sufficient Delta (δ)-ferritic effective nucleating point can not be provided, subsequent welding point solidified structure is caused Average grain diameter is more than 90 μm, and ductile-brittle transition temperature (DBTT) is more than -65 DEG C as a result, reduces low-temperature flexibility.
For example, Al-Ca-Ti-Mg-O system oxide includes TiO2、CaO、Al2O3, MgO etc., at this point, the Al-Ca- Ti-Mg-O system oxide meets following formula (2).
% (TiO2)+% (CaO) >=40------ formula (2)
When meeting the Ti minimum value of the formula (1), the formula (2) will be met, when not being able to satisfy the Ti of the formula (1) most When small value, it is unable to satisfy the formula (2).That is, passing through the condition control of Cr content, N content and Al content based on the formula (1) Ti value, thus % (TiO in Al-Ca-Ti-Mg-O system oxide2) and % (CaO) and can be 40% or more.As a result, By largely ensuring as the equiax crystal of welding point solidified structure or the advantageous CaO-TiN of the nucleating point of TiN2Phase, Neng Gouxi Change the average grain diameter of welding point solidified structure, improves low-temperature flexibility.
For example, Al-Ca-Ti-Mg-O system oxide meets following formula (3) to (5).
% (TiO2)+% (CaO)+% (Al2O3) >=80------ formula (3)
(% (TiO2)+% (CaO))/(% (TiO2)+% (CaO)+% (Al2O3)) >=0.4------ formula (4)
0.3≤% (CaO)/% (TiO2)≤0.8------ formula (5)
According to the formula (3), field trash when Al deoxidation is Al-Ca-Ti-Mg-O system, wherein % (TiO2), % (CaO) With % (Al2O3) overall ratio should be 80% or more.As % (TiO2), % (CaO) and % (Al2O3) overall ratio less than 80% When, stabilized is rich magnesium (MgO rich) oxide or Al2O3- MgO system oxide can not form CaO- effective to nucleation TiO2Phase.
According to the formula (4), the % (TiO relative to formula (2) and formula (3) is set2) and % (CaO) overall ratio % (TiO2), % (CaO) and % (Al2O3) overall ratio, in order to further largely ensure the equiax crystal as welding point solidified structure Or the advantageous CaO-TiO of nucleating point of TiN2Phase, when its ratio is less than 0.4, CaO-TiO2The ratio of phase is reduced, it is difficult to sufficiently Refine the average grain diameter of welding point solidified structure.
According to the formula (5), even if meeting the formula (3) and formula (4), as % (CaO)/% (TiO2) ratio is less than 0.3 When, the constituent of oxide is unable to fully ensure CaO-TiO advantageous to nucleation2, as % (CaO)/% (TiO2) ratio is more than When 0.8, oxide constituent translates into CaO-Al2O3Coarse low melting point oxide, thus translate into be nucleated it is invalid Oxide.
That is, the ferrite-group stainless steel of one embodiment of the present of invention meets the formula (2) to formula (5), and including maximum Diameter is 0.05 to 5 μm, has 9/mm2The Al-Ca-Ti-Mg-O system oxide of above distribution density.
Fig. 4 is the average crystalline substance for showing the welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention The chart of the measurement result of grain size.Fig. 5 be show one embodiment of the present of invention ferrite-group stainless steel based on welding % (CaO+TiO in the average composition ingredient of the oxide of the average grain size of connector solidified structure2) measurement result figure Table.
It is the solidification for determining the ferrite-group stainless steel welding point of examples and comparative examples of the present invention referring to Fig. 4 Organize the chart of the average diameter of crystal grain.That is, the equiax crystal size of the welding point of comparing embodiment and comparative example as a result, energy Enough confirmation embodiment is compared to comparative example, equiax crystal size refinement about 40% or so.Specifically, it can be seen that embodiment The average grain diameter of the welding point solidified structure of ferrite-group stainless steel is 90 μm or less.However, it is possible to find out, comparative example The average grain diameter of welding point solidified structure of ferrite-group stainless steel be more than 90 μm, specifically more than 100 μm.
That is, the crystal grain of the welding point solidified structure of the ferrite-group stainless steel of one embodiment of the present of invention is average Diameter can be 90 μm or less.
It is to measure the embodiment of the present invention using scanning electron microscope-power spectrum (SEM-EDS) analytical equipment referring to Fig. 5 With the % (CaO+TiO in the average composition ingredient of the oxide of the ferrite-group stainless steel of comparative example2) chart.
That is, the constituent of Welded Joints grain size and oxide, especially Welded Joints grain size and conduct CaO-TiO2The CaO phase and TiO in the source (source) of phase2The correlativity of the sum of phase is investigated, and result can be seen that As % (CaO+TiO2) when being 40% or more, it can be ensured that welding point grain size is 90 μm hereinafter, thin so as to realize Change, as % (CaO+TiO2) less than 40% when, welding point coarse grains.
Fig. 6 is the measurement knot for showing the welding point impact energy of the ferrite-group stainless steel of one embodiment of the present of invention The chart of fruit.Fig. 7 is the ductile-brittle transition for showing the welding point of ferrite-group stainless steel of one embodiment of the present of invention The chart of the measurement result of temperature (DBTT).
It is the chart for comparing the welding point impact energy of implementation column and comparative example referring to Fig. 6.It can be calculated and be prolonged by chart Property-brittle transition temperature (DBTT), the temperature of embodiment are cited as -74 DEG C, and the temperature of comparative example is cited as -54 DEG C.That is, with every On the basis of a DBTT, destruction becomes brittle break from ductile fracture, this is hair when processing welding point under cryogenic The main reason for raw crackle.Therefore, DBTT is preferably low temperature.
It is the ductile-brittle of the welding point of the ferrite-group stainless steel of examples and comparative examples of the present invention referring to Fig. 7 The measurement chart of transition temperature (DBTT).I.e., it is possible to find out, embodiment is compared to about low 20 DEG C or so of its DBTT of comparative example.
That is, the DBTT of the ferrite-group stainless steel welding point of one embodiment of the present of invention can be -65 DEG C or less.
In the following, by embodiment, further the present invention is described in detail.
Embodiment 1 to 12
By the stainless steel of the base material components system of the embodiment 1 to 12 including the following table 1 through electric furnace (EAF)-refining furnace (AOD)-adjustment of formula (LT)-tundish (Tundish)-continuous casting process and after manufacturing steel billet, hot rolling and cold rolling manufacture are thick Degree is the steel plate of 1.2mm.
Comparative example 1 to 12
By the stainless steel of the base material components system of the comparative example 1 to 8 including the following table 1 through electric furnace (EAF)-refining furnace (AOD)- Adjustment of formula (LT)-tundish (Tundish)-continuous casting process and after manufacturing steel billet, hot rolling and cold rolling manufacture with a thickness of The steel plate of 1.2mm.
Table 1
Later, in order to evaluate according to the embodiment and comparative example manufacture steel plate welding characteristic, using GTA technique into After row welding, grain size, welding point section and the surface analysis of welding point, hardness analysis are investigated, angstrom has stayed and to stretch (ericessen) test, welding point impact energy etc..To as the molten steel composition of major influence factors and its subscale Type and size distribution investigated, and indicate in the following table 2 and table 3.
Here, utilizing the type and size point of scanning electron microscope-power spectrum (SEM-EDS) analytical equipment measurement oxide Cloth, analysis method are amplified under 1000 times or more of multiplying power using lateral 1mm, the longitudinal direction 1mm area in the section to final products The size of oxide and the mode of ingredient are automatically determined, at least measures 5 regions or more, and indicate its average value.The oxygen of measurement The maximum gauge of compound is 5 μm, and having the oxide quantity greater than the diameter is largely 1/mm2Hereinafter, and to nucleation In vain, therefore, it is eliminated from calculating.
Table 2
Table 3
In order to ensured by the embodiment described one embodiment of the present of invention ferritic stainless steel mouldability and Low-temperature flexibility when disengaged (1), even if including components system, can not obtain the quantity of formula (2) and oxide, therefore, Ke Yizhi Dawn, it is unable to ensure the low-temperature flexibility of crystal grain refinement and welding point.
More specifically, moreover, mesh can be obtained by the ferrite-group stainless steel for meeting formula (3) to formula (5) Therefore mark oxide composition, size and distribution density could be aware that the low temperature for being unable to ensure crystal grain refinement and welding point is tough Property.
As described above, illustrate exemplary embodiment of the present invention, but the present invention is not limited thereto, technology belonging to the present invention The those of ordinary skill in field can carry out a variety of changes it will be appreciated that in the case where not departing from the concept and range of claims More and deform.

Claims (7)

1. a kind of ferrite-group stainless steel of welding point excellent in low temperature toughness, in terms of weight %, comprising: Cr:9~30%, N: Less than 0.015%, Al:0.005~0.04%, Ti:0.1~0.5%, surplus Fe and other inevitable impurity, and it is full Be enough following formula (1), and including diameter be 0.05 to 5 μm, have 9/mm2The Al-Ca-Ti-Mg-O system of above distribution density Oxide,
Ti > (0.0065Cr+0.38N+8.3Al) --- --- formula (1).
2. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to claim 1, wherein the stainless steel Include: C: less than 0.02%, Si:0.01~0.5%, Mn:0.01~0.5%, S: less than 0.01%, P: less than 0.04%, Ca: 0.0001~0.003%.
3. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to claim 1, wherein the stainless steel Including selected from one or more of the group being made of Mo:0.1~2.0%, Ni:0.1~2.0% and Cu:0.1~2.0%.
4. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to any one of claim 1 to 3, In, Al-Ca-Ti-Mg-O system oxide meets following formula (2),
% (TiO2)+% (CaO) >=40------ formula (2).
5. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to any one of claim 1 to 3, In, Al-Ca-Ti-Mg-O system oxide meets following formula (3) to (5),
% (TiO2)+% (CaO)+% (Al2O3) >=80------ formula (3)
(% (TiO2)+% (CaO))/(% (TiO2)+% (CaO)+% (Al2O3)) >=0.4------ formula (4)
0.3≤% (CaO)/% (TiO2)≤0.8------ formula (5).
6. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to any one of claim 1 to 3, In, the average grain diameter of welding point solidified structure is 90 μm or less.
7. the ferrite-group stainless steel of welding point excellent in low temperature toughness according to any one of claim 1 to 3, In, welding point ductile-brittle transition temperature (DBTT) is -65 DEG C or less.
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